To produce hydrocarbons from subterranean reservoirs, oilfield operators drill and at least partially case boreholes. For example, a shallow portion of the borehole may be promptly cased to protect the water table from possible contamination by hydrocarbons and drilling fluids, whereas deeper portions of the borehole may be later cased as needed to facilitate the drilling process or completion of the well.
Each borehole is typically cased with a steel casing string, i.e., continuous or threaded lengths of steel pipe lowered into the borehole before being cemented in place. Despite being made of steel and secured by cement, casing strings can fail. Among the many factors that may contribute to casing failure is internal casing wear. The main cause of such casing wear is the frictional rubbing of other tubular strings on the inner surface of the casing string. For example, as a drill string moves and rotates inside a casing string, it rubs against the inner surface of the casing string (often with extreme force), potentially reducing the wall thickness and thereby degrading the casing string's integrity and resistance to deformation.
Where such wear is accurately identified or predicted, corrective action can be taken to restore or preserve casing string integrity, e.g., by providing a liner and/or altering a drilling program to mitigate wear damage. Such corrective actions can avoid non-productive time and other forms of economic and/or environmental losses that can be caused by loss of casing integrity. Nevertheless, the accuracy of existing models for identifying and predicting casing wear appears, for many deviated well configurations, to be inadequate.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.